ASTM_D_6700-19.pdf

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recommendations isued by the World Trade Organization Technical Barriers to Trade(TBT)Committee.Designation:D6700-19INTERNATIONALStandard Guide forUse of Scrap Tires as Tire-Derived FuelThis standard is issued under the fixed designation D6700;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon(8)indicates an editorial change since the last revision or reapproval.1.Scope1.6 This international standard was developed in accor-1.1 This guide covers and provides guidance for the mate-dance with internationally recognized principles on standard-rial recovery of scrap tires for their fuel value.The conversionization established in the Decision on Principles for theof a whole scrap tire into a chipped formed for use as a fuelDevelopment of International Standards,Guides and Recom-produces a product called tire-derived fuel(TDF).This recov-mendations issued by the World Trade Organization Technicalery guide has moved from a pioneering concept in the earlyBarriers to Trade(TBT)Committee.1980s to a proven and continuous use in the United States with2.Referenced Documentsindustrial and utility applications.2.1 ASTM Standards:1.2 Combustion units engineered to use solid fuels,such asD2013/D2013M Practice for Preparing Coal Samples forcoal or wood,or both,are fairly numerous throughout the U.S.Many of these units are now using TDF even though they wereAnalysisD2361 Test Method for Chlorine in Coal(Withdrawn 2008)not specifically designed to burn TDF.It is clear that TDF hasD2795 Test Methods for Analysis of Coal and Coke Ashcombustion characteristics similar to other carbon-based solid(Withdrawn 2001)fuels.Similarities led to pragmatic testing in existing combus-D3172 Practice for Proximate Analysis of Coal and Coketion units.Successful testing led to subsequent acceptance ofD3173/D3173M Test Method for Moisture in the AnalysisTDF as a supplemental fuel when blended with conventionalSample of Coal and Cokefuels in existing combustion devices.Changes required toD3174 Test Method for Ash in the Analysis Sample of Coalmodify appropriate existing combustion units to accommodateand Coke from CoalTDF range from none to relatively minor.The issues of properapplications and specifications are critical to successful utili-D3175 Test Method for Volatile Matter in the AnalysisSample of Coal and Cokezation of this alternative energy resource.D3176 Practice for Ultimate Analysis of Coal and Coke1.3 This guide explains TDFs use when blended andD3177 Test Methods for Total Sulfur in the Analysis Samplecombusted under normal operating conditions with originallyof Coal and Coke(Withdrawn 2012)3specified fuels.Whole-tire combustion for energy recovery isD3178 Test Methods for Carbon and Hydrogen in thenot discussed herein,since whole-tire usage does not requireAnalysis Sample of Coal and Coke(Withdrawn 2007)tire processing to a defined fuel specification.D3179 Test Methods for Nitrogen in the Analysis Sample of1.4 The values stated in inch-pound units are to be regardedCoal and Coke(Withdrawn 2008)3as standard.The values given in parentheses are mathematicalD3682 Test Method for Major and Minor Elements inconversions to SI units that are provided for information onlyCombustion Residues from Coal Utilization Processesand are not considered standard.D4239 Test Method for Sulfur in the Analysis Sample ofCoal and Coke Using High-Temperature Tube Furnace1.5 This standard does not purport to address all of theCombustionsafety concerns,if any,associated with its use.It is theD4326 Test Method for Major and Minor Elements in Coalresponsibility of the user of this standard to establish appro-and Coke Ash By X-Ray Fluorescencepriate safety,health,and environmental practices and deter-D4749 Test Method for Performing the Sieve Analysis ofmine the applicability of regulatory limitations prior to use.Coal and Designating Coal SizeThis guide is under the jurisdiction of ASTM Committee D34 on Waste2 For referenced ASTM standards,visit the ASTM website,www.astm.org,orManagement and is the direct responsibility of Subcommittee D34.03 on Treatment,contact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMRecovery and Reuse.Standards volume information,refer to the standards Document Summary page onCurrent edition approved Feb.1,2019.Published February 2019.Originallythe ASTM website.approved in 2001.Last previous edition approved in 2013 as D6700-01(2013).3The last approved version of this historical standard is referenced onDOI:10.1520/D6700-19.www.astm.org.Copyright ASTM Intemational,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United StatesD6700-19D5468 Test Method for Gross Calorific and Ash Value of3.2.12 standard size specification,n-the size specificationsWaste Materials(Withdrawn 2016)with the broadest application when blending with other solidD5681 Terminology for Waste and Waste Managementfuels and requiring minimal adjustments or retrofits to existingD5865 Test Method for Gross Calorific Value of Coal andsolid fuel combustion units.Coke3.2.13 supplemental fuel,n-a combustible material thatE873 Test Method for Bulk Density of Densified Particulatedisplaces a portion of traditional fuel source.It refers to theBiomass Fuelsproduct being used in conjunction with another conventionalF538 Terminology Relating to the Characteristics and Per-fuel but typically not as a sole fuel supply.formance of Tires3.2.14 tire-derived fuel(TDF),n-a product made from2.2 EPA Standards:scrap tires to exact specifications of a system designed toSW-846-5050 Bomb Preparation Method for Solid Wasteaccept a tire-derived fuel as primary or supplemental fuelSW-846-9056 Determination of Inorganic Anions by lonsource.Chromatography3.2.15 wire,n-in a tire,high-tensile,brass-plated steel3.Terminologywire,coated with a special adhesion-promoting compound,used as tire reinforcement as belts,beads,or radial tire plies.3.1 Definitions-For definitions of general terms used in thisguide,refer to Terminologies D5681 and F538 on waste3.2.16 wire free,n-TDF that is free of all inherent wire.management and tires,respectively3.2.17 X minus,n-a designation of sample particle size,3.2 Definitions of Terms Specific to This Standard:with Dimension X indicating the upper limit or maximum size3.2.1 bead wire,n-a high-tensile steel wire,surrounded byof particles passing through a sieve or screen opening uponrubber,which forms the bead of a tire that provides a firmwhich is cumulatively retained less than or equal to 1%of thecontact to the rim.sample.For example,a sample designated as 2 in.(5 cm)minus would pass a 2-in.screen opening with less than or3.2.2 chip size,n-the dimension of size-reduced rubberequal to 1%of the sample retained.particles resulting from the processing of whole tires.3.2.3 combustion,n-the chemical reaction of a material4.Significance and Usethrough rapid oxidation with the evolution of heat and light.4.1 When considering the specification of fuels for a boiler,3.2.4 combustion unit,n-any number of devices to produceissues to evaluate are the fuels combustion characteristics,or release energy for the beneficial purpose of production byhandling and feeding logistics,environmental concerns,andburning a fuel to include,but not limited to,units such asash residue considerations.A thorough understanding of theseindustrial power boilers,electrical utility generating boilers,issues is required to engineer the combustion unit for powerand cement kilns.and steam generation;however,TDF has demonstrated com-3.2.5 energy value,n-the assignment of a value to thepatible characteristics allowing it to serve as a supplementaltire-derived fuel as measured in British thermal units per poundfuel in existing combustion units based on cumulative experi-or calories per gram.ence in many facilities originally designed for traditional fossilfuels,or wood wastes,or both.When used as a supplemental3.2.6 fuel value,n-the heat content,as measured in Britishenergy resource in existing units,TDF usage is generallythermal units(Btu)/lb or cal/g.limited to blend ratios in the 10 to 30%range based on energy3.2.7 new tire,n-a tire that has never been mounted on ainput.This limit is due to its high heat release rate and lowrim.moisture content,which differ significantly from other solid3.2.8 relatively wire free,n-TDF that has a bead wirefuels such as wood,refuse-derived fuel,coal,and petroleumcontent not greater than 1%by weight,and a total wire contentcoke.of 2%or less by weight.4.2 New combustion units dedicated to the use of TDF(or3.2.9 rubber;n-an elastomer,generally implying naturalwhole tires)as the sole fuel source are rare.The generation andrubber,but used loosely to mean any elastomer,vulcanized andavailability of scrap tires are ultimately determined by marketnot vulcanized.By definition,rubber is a material that isconditions for new tires and the depletion rate of scrap tirecapable of recovering from large deformations quickly andinventories(stockpiles).Scrap tires account for approximatelyforcibly and can be,or already is,modified to a state in which1%of the municipal solid waste stream.Based on a nationalit is essentially insoluble in a boiling solvent.scrap tire generation rate,there are roughly 2.5 to 3 million3.2.10 scrap tire,n-a rubber tire that is no longer used fortons(annually available for all uses to include fuel,crumbits originally intended application.rubber,engineering projects,and so forth).Some dedicated3.2.11 screen,n-an apparatus for separating sizes of gran-combustion units have been built,however,competition for theules.scrap tires as other existing sources begin to use TDF willdetermine the ultimate viability of these facilities.Althoughmost regions can supply TDF demand as a supplemental fuel,a dedicated boiler in the range of 500 000 lb/h(227 000 kg/h)Available from United States Environmental Protection Agency(EPA),WilliamJefferson Clinton Bldg.1200 Pennsylvania Ave.,NW,Washington,DC 20460.steaming capacity would require over 66 000 scrap tires/day tohttp:/www.epa.gov.meet its fuel demand.Such demand may strain a regions24D6700-19ability to supply and put the fuel supply at risk.Some design5.Tire-Derived Fuel Analysis-General Descriptionprojects have incorporated TDF as a supplemental fuel with5.1 TDF is defined as a fuel source derived from thewood,coal.coke.sludge,or some combination of multipleprocessing of scrap tires into rubber chips with a range in sizefuels where demand is consistent with supply availability.and metal content.Processing may include shredding.4.3 It is important to understand what objectives may lead tochopping,classification,recycling.granulation,wire/fabricTDFs choice as a supplemental fuel in existing power units.separation,and other technologies.Size normally varies in aSeveral model objectives may be as follows:range from 1 in.(2.5 cm)to 4 in.(10.2 cm).Metal content4.3.1 To increase boiler efficiency in a co-fired boiler usingranges from wire free,to relatively wire free,to only bead wirewood,sludge,and coal:removed,to no wire removed.TDFs tolerable wire content is4.3.2 To procure a competitively priced fuel;determined by a combustion units design considerations.4.3.3 To supplement limited supplies of an existing fuel:TDFs wire removal is determined by production process4.3.4 To use a high-quality fuel:capabilities.Some combustion units such as cement kilns can4.3.5 To achieve environmental benefits by using a fuel withtolerate all inherent wire,so no removal is necessary.Incircumstances where no effort is made to remove wire.TDFa relatively low sulfur content in comparison to certain coals orpetroleum coke,and;must be cleanly cut with minimal exposed wire protrusion fromthe chips to facilitate mechanical handling.4.3.6 To provide a public and social benefit that solves aregional solid waste problem.5.2 Unless temperatures in a combustion unit are sufficientto oxidize the wire,the energy contribution from the wire is4.4 Boilers generally are engineered around fuels that willnominal and will account for a lower product energy value thanbe available through the amortized life of the power unit.that of either a wire-free or relatively wire-free TDF product.Boiler design discussions here are limited as TDF standard sizeCement kilns typically burn at sufficient temperatures tospecifications have been developed to ensure TDFs perfor-oxidize the wire and benefit from both the energy release frommance in existing systems.TDF is mined from the solid wasteoxidation and the resultant iron oxide that becomes a criticalstream as a whole tire,then engineered via processing tech-component in cement chemistry.Depending on the amount ofniques to fit a new or existing combustion unit.A majorwire removed,the TDF has an energy content ranging frommodification or re-engineering of the combustion unit to14000to15500Btu/1b(7770to8600cal/g).accommodate TDF normally would make its use uneconomicalas a supplemental fuel.TDFs use is economically dependent5.3 Combustion efficiency for TDF generally is understoodon the following two issues:to be in the 80%range.TDF represents an ideal fuel source in4.4.1 A combustion units existing ability to use the fuelthat its moisture content is low(I to 3%).and its energy valuewithout modification(other than minor operational changes inis high.Low moisture content uses less energy for moistureoxygen grate speed adjustments,and feed/material handling)vaporization and lowers combustion gas mass flow rate.TDFand,has a volatile content of roughly 66%,which indicates rapidheat release.Relatively low ash content(3 to 5%maximizes4.4.2 The ability of a supplier to economically collect,heat absorption and decreases ash disposal costs.As rubber isprocess,and transport TDF to the combustion unit.non-absorbent,moisture swings during seasonal periods of4.5 Once an economic decision has been made to developrainfall in ambient weather conditions are limited to a range ofTDF as a fuel source for a particular unit,issues of fuel1 to 8%The smaller the TDF chip size,the greater the storagespecifications including size,proximate and ultimate analysis.pile surface area and its concomitant ability to hold moisture oncombustion characteristics,and environmental concerns mustits surface.Table I identifies the energy content of commonbe evaluated properly to determine whether TDF is an appro-fuel types currently used singularly or in some combination.priate supplemental fuel resource without major system modi-5.4 The specifications for TDF are somewhat customerfication.specific,as this material will be fed into an existing combustionunit.A highly refined product with the wire removed is moreexpensive to produce,but provides more energy per ton andfewer operating problems in many units.Problematic areas to田GasTABLE 1 Energy Value01Energy Value in million Btu/short3TDFFuel Typeton(MBTU/ton)国CokeTire-derived fuel(TDF)28-325B CoalPetroleum coke(PC)26-28Bituminous coal(BC)18-27S CoalSubbituminous coal(SC)17-2515L CoalLignite coal(LC)12-14Wood(wet)Wood fuel(WF)8-17Relative Comparison of Non-Solid Fuels013438Gas42-48FIG.1 Relative Energy Comparison of Fuels(Scale in Btu/ton)D6700-19Sampling LogTDF Size Specification-TestingPlease complete the following and include with the sample shipped.Send additionalcopies to:Plant Location:Name of Sampler:Title of Sampler:Time Samples Taken:Date Samples Taken:Total of nine(9)Samples Taken:Yes NoTotal weight of sample sent,all nine(9)samples combined:Ibs.Number of boxes shipped to make up complete sample:boxes(preferably one)Additional notes:Signature:Date:FIG.2 Sampling LogTABLE 2 Analysis of TDF(Relatively Wire Free)evaluate to determine true specification requirements are fuelfeed system,grate maintenance,ash circulation/handling,andNoTE 1-TDF produced from scrap tires with 96%plus wire removed.ash disposal systems.Since roughly 10 to 15%of a tire isDescriptionPercent by Weight as Receivedcomprised of radial ply wire and bead wire,any TDF that is notProximate AnalysisMoisture0.474relatively wire free will have a fuel value 10 to 15%less thanAsh4.22the values reported for TDF in Table 1.TDF specified to haveVolatile matter65.34a lower wire content is more expensive to produce.TheFixed carbon29.966Total 100.00increased cost is attributable to further refinement expense andUltimate Analysisultimate disposal,or recovery cost for the wire residue gener-Moisture0.47ated from TDF production,or both.Ash4.22Carbon89.515.5 In addition to steel wire,nylon and polyester may beHydrogen7.59used in tire construction.Nylon and polyester plies are found inNitrogen0.27Sulfur1.92both steel radial and non-steel radial tires,passenger,and truckOxygentires.Approximately 3%of a tire is made up of these types ofElemental AnalysisZinc1.52non-steel plies.When a tire is processed into TDF,theseCalcium0.378synthetic plies will typically stay in the TDF.Both nylon andIron0.321polyester are petrochemical products with an energy contentChlorine0.149Chromium0.0097similar to that of rubber.Due to their low ash content and highFluoride0.0010energy content,the fuel value of plies is relatively consistentCadmium0.0006with that of the rubber.Lead0.0065Others below detectable levels to include mercury,barium,silver,and so5.6 A representative analysis of TDF is presented in Table 2.forthThis table identifies key combustion issues.The high amountTheoretical air3.362 kg/10000 Btu(2520 Kcal)of fixed carbon(29.96%)suggests particulate concerns andWet gas from fuel0.266 kg/10000 Btu(2520 Kcal)ash(4.22%)suggests solid waste concerns.Other elements ofH2O from fuel0.179 kg/10000 Btu(2520 Kcal)concern include sulfur(1.92%)and zinc(1.52%).6.Handling Considerations Conveying,Grate,and Ashgreater percentage of inherent wire the chip size must ulti-6.1 TDF can be produced with the wire left in or taken out.mately be smaller,in the s-in.(1.6 cm)to 2-in.(5.08 cm)sizeEither way,one must balance the trade-off(s).To remove a range.Both smaller chip size and increased wire removal willD6700-19add to the cost of producing TDF.Smaller chip requiressufficient temperature is achieved,normally above ironsincreased mechanical production time.Wire residue may bekindling point of about 1500 F(815 C).In any event,it willlandfilled or recovered,adding to production costs.Wireremain on the grate as either wire or iron oxide unlessrecovery potential is dependent on regional,market,andunder-fired air velocity through the grate is sufficient to entrainquality factors,but market value may not fully offset recoverythe fine wire with the air flow.Iron will not fume,but it willcosts.generate heat if converted to the iron oxide form,roughly6.2 Wire Removal Precludes the Following Potential Prob-3000 BtuAb(1665 cal/g).It is unlikely that grate temperatureslems:in stoker boilers will exceed 1000F(538C)without other6.2.1 Wires protruding from TDF may cause chips to clumpsignificant grate problems developing.together,causing distribution problems.TDF is not as flowable6.6 As a case study to illustrate potential problems with wirewhen long strands of exposed wire are present.in a fluid bed combustor,a pilot facility tested a 100%wire-in6.2.2 Wires protruding from a rubber chip may catch on fuelrubber chip for developmental evaluations.These tests wereconveying systems.conducted for a large midwestern utility that currently is using6.2.3 Wires may trip any metal detector used to protect thea commercially scaled unit for power production and wascombustion unit from metal contamination.seeking to introduce tire-derived fuel,wire in,as a standard6.2.4 Wires in rubber chips would either be captured orfuel source.The pilot plant initially had been equipped with therejected by magnet(s)used to protect the combustion unit fromstandard sparge pipe/dual cone air distributor and bed cleans-metal contamination.Fixed magnets will require greater fre-ing system.When running with 100%tire chips,it wasquency of cleaning.discovered that the bed draw-down capabilities were impaired6.2.5 Significant amounts of wire may slag on the grate.by the hang-up of wires in the holes of the inner cone.AfterThere is a higher risk of this occurring on fixed-grate combus-two days of operation,all of the holes were plugged.tion units.Ultimately,retrofits made to the pilot plant to accommodate the6.2.6 In the case of a moving grate,the wire may fallwire-in material included a conical air distributor to keepbetween the grate slats(posing a risk to grate keys),or lodgeeverything in the conical section fluidized and remove restric-between the slats(potentially chipping the grate upon its returntions to bed material flow where the wire could accumulate.on the underside if caught in a pinch point),or both.Subsequently,long-term use of a relatively wire-free TDF has6.2.7 Wires may cause problems in ash handling systems bybeen developed in several fluid bed combustors withoutplugging conveying systems,or problems in storage bins byretrofits.clumping or nesting.6.7 TDF in a size range of 2-in.(5.08 cm)minus is normally6.2.8 Wires will add to the total volume of ash disposal andcompatible with wood fuel and stoker coal in conveying tomay complicate disposal opportunities such as land spreading.conventional stoker boilers,thus allowing for easy introduction6.2.9 In a fluid bed boiler,wires may compromise ashonto an existing feeding system.Large pieces of rubber may beremoval by plugging,bridging,nesting,or a combinationrejected or sent to a hammer mill for further size reduction viathereof.screening systems used to reject oversized coal or wood fuel,if6.2.10 Significant amounts of wire may increase erosion insuch systems are in place.Oversized pieces should be avoideda circulating fluidized bed if wire becomes entrained in theunder these circumstances due to a hammer mills or coalcirculating bed medium.crushers difficulty in processing tire chips.6.3 With the wire removed,the ash content of TDF is from6.8 A storage pile of TDF can mimic coal in appearance3 to 5%,while the ash content if all the wire remains typicallyfrom a distance,but does not create dusting concerns when leftis 14 to 18%.A TDF specification requiring all the bead wirein the open unprotected.TDF storage piles,if of sufficient size,and 50%of the radial ply wire to be removed should precludemay experience heating problems similar to coal piles.Storagethe problems identified in 6.2,and should achieve a standardmanagement should be similar to that of coal to precludesize specification that is relatively wire free.Specific or uniqueheating problems.boiler designs considered on a case-by-case basis to precludeproblems as noted.7.Combustion6.4 Tire wire consists of 99.9%iron.Left in the TDF,bead7.1 One way of optimizing combustion of TDF is to addresswire will remain in its wire form with very little or no change,the size of the tire pieces and ultimately its distribution on theas its mass is too great and the grate or bed temperature isgrate.Even distribution on the grate will occur if the currentinsufficient to cause oxidation.If significant quantities accu-solid fuel stoker is achieving even distribution with historicalmulate and temperatures are hot enough,partial oxidation mayfuels and if TDF is close in size and bulk density to historicaloccur which can lead to agglomeration where contact pointsfuel(s)so that it mimics fuel handling characteristics.Free-with other wire strands may fuse together.flowing TDF has a bulk density in the range of 25 to 30 lb/ft36.5 All bead wire essentially becomes part of the grate ash.(4 to 4.8 g/cm3).Irons melting point is approximately 2800F(1537C).7.2 Although one could produce a rubber particle smallRadial ply wire has essentially the same iron content as beadenough to fire in a pulverized coal boiler with a blended mix ofwire,but has a much smaller diameter.This wire may or mayTDF/coal,the cost to process TDF to meet a pulverized coalnot oxidize.Due to its low mass,rapid oxidation will occur ifspecification would be prohibitive.For example,an electrical5